Or you just got lucky with the environment where you were a child and didn’t realise how you were preferring to spend time with worse people over time, blaming the environment for it.
The problem is so pervasive that it isn't even noticeable. And now grown adults with high school level mentality and professional development having children who are also adults and were, of course, raised with the same bad ideas.
Have you never heard the complaint that there's no service anymore? No loyalty anymore? And no good communication anymore? It's something old people say and it's true.
Same for other professional services - businesses regularly offer discounts to new customers but not existing ones. Why should I stick with my bank, insurers or credit card when there are more advantages to churning?
The premise of the author is that today's grownups are terrible (adolescent behavior and attitudes) because of the changes brought about by high school becoming a thing. He's complaining about my generation, not saying it's better.
The "better" (behaved) people are over 75 or dead.